Knappert taught in Leuven and London, as well as several African universities. He also participated in several Esperanto conventions in the 1970s, such as TEJO.

Dr. Jan Knappert was Lecturer of Bantu Languages at the School of Oriental and African Studies, specializing in Swahili traditional and religious literature. He wrote extensively about the manuscripts he collected and deposited in the SOAS Archives. His most important contributions include Four Centuries of Swahili Verses (1979), Swahili Islamic Poetry (1971), Epic Poetry in Swahili and other African Languages, (1983), A Survey of Swahili Islamic Epic Sagas (1999). He also resided at the University of Dar es Salaam where he became Secretary of the East African Swahili Committee as well as Editor of the Journal of the same committee, after the death of W.H. Whiteley, in the 1970s. At SOAS, he worked with the great Africanists Malcolm Guthrie, A. N. Tucker, B. W. Andrzejewski, Gordon Innes, and Ronald Snoxall. In addition to the study of Swahili, Dr Knappert also holds a degree in Sanskrit with Indian history, Hinduism and Buddhism, a degree in Semitic languages with Hebrew, Arabic and Islam, and a Master in Austronesian studies, with Malay, Tagalog, Hawaiian and Malagasy. After teaching at SOAS for a number of years, he moved to Belgium to lecture. After this he retired from the University of Louvain, Belgium, to devote himself entirely to writing.